Electromagnetic device



April 30, 1968 c, w H s 3,381,250

ELECTROMAGNETIC DEVICE Filed June 2'7, 1966 29 /6 50 30 y I a 1/1 [/1 V A I 28 3% FIG. 2. @712 FORCE POUNDS STROKE 'PER UNIT United States Patent 3,381,250 ELECTROMAGNETIC DEVICE Leland Clay Weathers, Plymouth, Mich., assignor to Sperry Rand Corporation, New York, N.Y., a corporation of Delaware Filed June 27, 1966, Ser. No. 560,402 3 Claims. (Cl. 335-255) ABSTRACT OF THE DISCLOSURE A solenoid has a stationary pole piece which has a frusto-conical recess and a smaller diameter cylindrical recess with a transversely-directed shoulder intermediate and abutting the said frusto-conical recess and the said smaller diameter cylindrical recess, has an armature with a frusto-conical surface that is complementary to the said frusto-conical recess in the said pole piece and with a small diameter cylindrical surface that is complementary to the said smaller diameter cylindrical recess in the said pole piece and with a transversely-directed shoulder that is intermediate and abuts the said frustoconical surface and the said small diameter cylindrical surface, has a tube which guides and confines the said armature for movement relative to the said pole piece, and has a winding which can be energized to cause the said armature to move relative to the said pole piece. The transversely-directed shoulder on the armature confronts the transversely-directed shoulder on the pole piece, but the spacing between those transversely-directed shoulders is always greater than the spacing between the said frusto-conical surface on said armature and the said frusto-conical recess in the said pole piece to prevent engagement between those transversely-directed shoulders.

This invention relates to improvements in electromagnetic devices. More particularly, this invention relates to improvements in solenoids.

It is, therefore, an object of the present invention to provide an improved solenoid.

The lengths of the strokes of the armatures of solenoids are usually quite short. Customarily, armatures of the said solenoids are initially spaced short distances away from the pole pieces of the said solenoids, and the windings of the said solenoids must be energized to move the said armatures toward the said pole pieces. When the said armatures are in their initial positions, the effective valuesof the pulls which the magnetic flux lines from the windings apply to the said armatures are small; but those values increase materially as the said armatures approach the pole pieces of the said solenoids. Frequently, the armatures apply hammer-like blows to the pole pieces of the solenoids as they move into engagement with the said pole pieces. It would be desirable to provide a solenoid which has a longerthan-usual stroke, which required a smaller-than-usual magnetizing force to move the armature thereof, and which applied smaller-than-usual forces to the armature thereof as the said armature approached the pole piece thereof. The present invention provides such a solenoid; and it does so by utilizing a combination cylindrical and frusto-conical magnetic gap between the armature and the pole piece thereof. It is, therefore, an object of the present invention to provide a solenoid which has a combination cylindrical and frusto-conical magnetic gap between the armature and the pole piece thereof.

Other and further objects and advantages of the present invention should become apparent from an examination of the drawing and accompanying description.

In the drawing and accompanying description, a preferred embodiment of the present invention is shown 3,381,250 Patented Apr. 30, 1968 and described but it is to be understood that the drawing and accompanying description are for the purpose of illustration only and do not limit the invention and that the invention will be defined by the appended claims.

In the drawing, FIG. 1 is a vertical section through one preferred embodiment of solenoid that is made in accordance with the principles and teachings of the present invention,

FIG. 2 is a sectional view, on a larger scale, through a portion of the magnetic gap between the armature and pole piece of the solenoid of FIG. 1, and

FIG. 3 is a graph which shows the difference between the force-stroke performance of the solenoid provided by the present invention and the force-stroke performance of a standard inverse-gap solenoid of comparable size.

Referring to the drawing in detail, the numeral 20 denotes a housing for one preferred embodiment of solenoid that is made in accordance with the principles and teachings of the present invention. The housing 20 will be made from magnetic material; and it will preferably be made from cast iron. The numeral 22 denotes a cylindrical recess within the housing 20, and the said recess extends inwardly from the left-hand face of that housing. A smaller-diameter cylindrical recess 24 extends inwardly from the inner end of the recess 22 and the said recesses are concentric. A small annular recess 26 is formed within the housing 20, and that recess communicates with the cylindrical recess 24. A cylindrical passage 28 extends through the housing 20 to the right from the cylindrical recess 24.

The numeral 29 denotes a tube of non-magnetic material; and one end of that tube is pressed into position within the cylindrical recess 24 in the housing 20. The other end of tube 29 projects outwardly beyond the lefthand face of the housing 20. The numeral 30 generally denotes the pole piece of the solenoid of FIG. 1; and the outer periphery of that pole piece is cylindrical. The pole piece 30 is dimensioned to fit snugly within the tube 29; and, preferably, the fit between the pole piece 30 and the tube 29 will be a press fit.

A passage 32 extends through the pole piece 30; and that passage communicates with a larger-diameter cylindrical recess 34. A frusto-conical recess 36 extends inwardly from the left-hand end of the pole piece 30, and the inner end of the recess 36 is spaced from the cylindrical recess 34 in pole piece 20 by a radially-directed shoulder 38. The angle of generation of frusto-conical recess 36 is about thirty degrees.

An O-ring 40 of resilient material is disposed within the annular recess 26 in the housing 20. That O-ring will be under compression whenever it is disposed within recess 26 and is hearing against the walls of recess 26 and the periphery of the tube 29. The O-ring 40 will provide a liquid-tight seal between the housing 20 and the tube 29, and will thus keep water from passing between the said housing and the said tube to reach the recess 22.

A coil form 42 of annular form has a winding 44 wound thereon. That coil form is dimensioned to fit within the cylindrical recess 22 in the housing 20 and to telescope over the periphery of the tube 29. Preferably, the coil form 42 will fit snugly within the annular space defined by the cylindrical recess 22 and the periphery of the tube 29. An end wall 46 abuts the left-hand face of the housing 20, and also abuts the left-hand face of vthe coil form 42. As a result, the end wall 46 will help hold the coil form 42 solidly in position within the housing 20. The end wall 46 has a cylindrical opening therein; and that opening will fit snugly over the left-hand end of the tube 29.

The numeral 48 generally denotes the armature for the solenoid of FIG. 1. The armature 48 is generally cylindrical in configuration, but it has a frusto-conical recess 56 in the left-hand end thereof. The armature 48 has a frusto-conical surface 50 at the right hand end thereof which is complementary to, and which is in register with, the frusto-conical recess 36 in the pole piece 30. The angle of generation of frusto-conical surface 50 is about thirty degrees. A cylindrical surface 52 is provided on the righthand end of the armature 48; and that cylindrical surface is in register with, and is dimensioned to telescope within, the cylindrical recess 34 in the pole piece 30. A radiallydirected shoulder 54 is provided on the armature 48 intermediate the frusto-conical surface 50 and the cylindrical surface 52. The radially-directed shoulder 54 is in register with the radially-directed shoulder 38 on the pole piece 30. A valve rod 58 is disposed within an axially-extending passage at the geometric center of the armature 48; and that valve rod is fixedly secured to that armature. The right-hand end of valve rod 58 has a conical face 60.

A closure 62 is disposed within the cylindrical opening in the end wall 46; and the right-hand portion of closure 62 has a reduced diameter to tacilitate the telescoping of that right-hand portion into the left-hand end of the tube 29. An annular recess 64 is formed in the reduceddiameter right-hand portion of the closure 62; and an O-ring 66 of resilient material is disposed within recess 64. The O-ring 66 will be under compression whenever it engages the walls of the annular recess 64 and the inner surface of the tube 29. The right-hand face of the reduced-diameter right-hand portion of the closure 62 will act as a stop for the armature 48. The tube 29 will guide and confine armature 48 as it moves toward and away from that right-hand portion of closure 62.

The numeral 68 denotes a valve body which is fixedly disposed within the cylindrical passage 28 through the housing 20; and valve body 68 has a valve seat 70 which is engageable by the conical face 60 on the valve rod 58 to prevent movement of fluids through passage. Movement of that conical face 60 away from valve seat 70 will permit movement of fluids through passage 28. A helical compression spring 72 is disposed within the cylindrical recess 34 in the pole piece 30; and the left-hand end of spring 72 bears against the right-hand end of the armature 48 to bias that armature toward the position shown by FIG. 1. However, spring 72 can yield, whenever the winding 44 is energized, to permit the armature 48 to move to the right in FIG. 1. As armature 48 so moves, it will move the conical face 60 of the valve rod 58 into sealing engagement with the seat 70 on the valve body 68.

The numeral 74 in FIG. 3 denotes the force-stroke curve of a standard inverse-gap solenoid which has a winding that is identical to the winding 44 and which has an armature with the same diameter and weight as the armature 48. The numeral 76 in FIG. 3 denotes the 'forcestroke curve provided by the solenoid of FIG. 1.

The housing 20, the end wall 46, the armature 48, 'and the pole piece 30 are all made of magnetic material. As a result, whenever the winding 44 is energized, magnetic lines of flux will flow across the magnetic gaps between the armature 48 and the pole piece 30 to urge the said armature toward the said pole piece. The frusto-conical configurations of the surface 50 and of the recess 36 enable the armature 48 to have a length of stroke that is about one-third longer than the length of stroke of the armature of a standard inverse-gap solenoid of the same size.

It will be noted that the radial distance between the cylindrical surface 52 on the armature 48 and the surface of the cylindrical recess 34 in the pole piece 30 remains unchanged as armature 48 moves. As a result, cylindrical surface 52 and cylindrical recess 34 coact to define a substantially linear magnetic gap for the solenoid of FIG. 1. The frusto-conical surface 50 on the armature 48 coacts with the frusto-conical recess 36 in the pole piece 30 .4 to provide a frusto-conical magnetic gap for the said solenoid; and the said frusto-conical magnetic gap coacts with the substantially linear magnetic gap, provided by the cylindrical surface 52 and the cylindrical recess 34, to enable the solenoid of FIG. 1 to provide the forcestroke curve 76 in FIG. 3. That force-stroke curve is essentially flat-the force on the armature 48 having a value of approximately seven pounds when armature 48 is in the position shown by FIG. 1 and having a value of approximately eight pounds when that armature has moved through about nine-tenths of its length of stroke. In contrast, the force-stroke curve of a standard inversegap solenoid of the same size as the solenoid of FIG. 1 is far from flat. When the armature of such a solenoid is in its initial position, the force on that armature is less than six pounds; but, after that armature has moved through about nine-tenths of its length of stroke, the force on that armature is about twenty-six pound-s. This means that a standard inverse-gap solenoid, which uses a winding identical to the winding 44 and which has an armature of the same diameter and weight as the armature 48, will provide a lesser initial pull and will provide a far greater final pull for that armature than will the solenoid of FIG. 1. As a result, the ratio between the finaLto-initial forces on the armature 48 is less than two, whereas the ratio between the final-to-initial forces on the armature of a standard inverse-gap solenoid of the same size is more than four. This is very important; because it enables the solenoid provided by the present invention to initiate closing of the valve more rapidly than can a standard inverse-gap solenoid of the same size, and it keeps the solenoid provided by the present invention from applying the hammer-like blows to the conical face 60 and to the valve seat which such an inverse-gap solenoid would apply. All of this means that the solenoid provided by the present invention is a relatively longstroke, high efiiciency, long-lived solenoid.

The armature 48 and the pole piece 30 will preferably be plated with a protective layer to make the said armature and the said pole piece resistant to corrosion. Also, the non-magnetic tube 29 should be made from a material that is resistant to corrosion.

Whereas the drawing and accompanying description have shown and described a preferred embodiment of the present invention, it should be apparent to those skilled in the art that various changes may be made in the form of the invention without affecting the scope thereof.

What I claim is:

1. An electromagnetic device that comprises:

(a) a stationary path for magnetic flux lines which includes a stationary pole piece member,

(b) an armature member,

(c) a surface that supports said armature member and that: permits said armature member to move relative to said stationary pole piece member, and

(d) a winding that can cause magnetic flux lines to flow through said path and through said armature member to move said armature member relative to said stationary pole piece member,

(e) one of said members having a recess therein and the other of said members having an end that is complementary to said recess,

(f) said recess in said one member having a portion thereof of frusto-conical configuration and having a smaller diameter portion thereof of cylindrical configuration and having a transversely-directed shoulder intermediate and abutting said frus'to-conical portion and said smaller diameter cylindrical portion, said transversely-directed shoulder abutting and extending inwardly from the small diameter portion of said frusto-conical portion, and said smaller diameter cylinder portion abutting and extending axially from the small diameter portion of said transversely-directed shoulder,

(g) said one end of said other member having a frustoconical surface that is in register with, and that is complementary to, said frusto-conical portion of said recess in said one member,

(h) said one end of said other member having a cylindrical surface that is slightly smaller than but that is substantially complementary to said smaller diameter cylindrical portion of said recess in said one member and having a transversely-directed shoulder intermediate and abutting said frusto-conical surface and said cylindrical surface, said transversely-directed shoulder abutting and extending inwardly from the small diameter portion of said frusto-conical surface, :and said cylindrical surface abutting and extending axially from the small diameter portion of said transversely-directed shoulder,

(i) said smaller diameter cylindrical portion of said recess in said one member coating with said cylindrical surface on said one end of said other member to provide a substantially linear magnetic gap,

(j) said frusto-conical portion of said recess in said one member and said frusto-conical surface on said one end of said other member coating to provide a frusto-conical magnetic gap,

(k) said substantially linear magnetic gap and said frusto-conical magnetic gap coacting to provide (a) an initial force on said armature member, whenever said winding is energized and said armature member is spaced from said pole piece member,

(1) said substantially linear magnetic gap and said frusto-conical magnetic gap coacting to provide a final force on said armature member, whenever said winding is energized and said armature is closely adjacent said pole piece member, said final force having a ratio relative to said initial force of less than two,

(m) said transversely-extending shoulder on said one end of said other member confronting, but being spaced from, said transversely-extending shoulder in said recess in said one member,

(n) said tnansversely-extending shoulder on said one end of said other member being spaced from said transversely-extending shoulder in said recess in said one member a distance greater than the spacing between said frusto-conioal surface on said one end of said other member and said frusto-conical portion of said recess in said one member, whereby said transversely-extending shoulder on said one end of said other member will always be out of engagement with said transversely-extending shoulder in said recess in said one member.

2. An electromagnetic device as claimed in claim 1 wherein said surface that supports said armature is the interior of an elongated tube, wherein said tube confines and guides said armature for axial movement, and wherein a spring is disposed within said cylindrical portion of said recess in said one member and bears against said other member to urge said other member away from said one member.

3. An electromagnetic device as claimed in claim 1 wherein said one member is said stationary pole piece member, wherein said other member is said armature member, wherein a spring biases said armature member away from said pole piece member, and wherein said magnetic flux lines from said winding can move said armature member toward said pole piece member.

References Cited UNITED STATES PATENTS 1,436,639 11/ 1922 Bindschedler 335262 2,388,696 11/1945 =Lacart et a1. 335- 266 XR 3,241,006 3/1966 Boyko 335Z73 3,303,445 2/ 1967 Flentge 335255 BERNARD A. GILHEANEY, Primary Examiner.

G. HARRIS, Examiner. 

